Average Problems and Solutions

• 15. Average of five numbers is 27. If one number is excluded the average becomes 25. The excluded number is

  1. 35
  2. 45
  3. 55
  4. 65

  Answer :

  Option A

  Explanation:

  Number is (5*27) - (4*25) = 135-100 = 35

• 16. A library has an average of 510 visitors on Sundays and 240 on other day. The average number of visitors in a month of 30 days starting with sunday is

  1. 280
  2. 285
  3. 290
  4. 295

  Answer :

  Option B

  Explanation:

  As the month begin with sunday, so there will be five sundays in the month. So result will be:
  \begin{aligned}
  = (\frac{510 \times 5 + 240 \times 25}{30})
  = (\frac{8550}{30}) = 285
  \end{aligned}

• 17. A batsman makes a score of 87 runs in the 17th match and thus increases his average by 3. Find his average after 17th match

  1. 36
  2. 37
  3. 38
  4. 39

  Answer :

  Option D

  Explanation:

  Let the average after 17th match is x
  then the average before 17th match is x-3
  
  so 16(x-3) + 87 = 17x
  => x = 87 - 48 = 39

• 18. A motorist travel to a place 150 km away at an avearge speed of 50 km/hr and returns ar 30 km/hr.His average speed for the whole jouney in km/hr is

  1. 36.5 km/hr
  2. 37.5 km/hr
  3. 35.5 km/hr
  4. 34.5 km/hr

  Answer :

  Option B

  Explanation:

  Average speed will be
  \begin{aligned}
  \frac{2xy}{x+y} km/hr
  \end{aligned}
  
  = \frac{2(50)(30)}{50+30} km/hr
  = 37.5 km/hr

• 19. Average of 10 numbers is zero. At most how many numbers may be greater than zero

  1. 0
  2. 1
  3. 5
  4. 9

  Answer :

  Option D

• 20. The average age of husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. The present age of the husband is

  1. 40
  2. 35
  3. 45
  4. 55

  Answer :

  Option A

  Explanation:

  Sum of the present ages of husband, wife and child = (27 * 3 + 3 * 3) years = 90 years.
  
  Sum of the present ages of wife and child = (20 * 2 + 5 * 2) years = 50 years.
  
  Husband's present age = (90 - 50) years = 40 years

• 21. The average score of a cricketer for ten matches is 38.9 runs. If the average for first six matches is 42, then average for last four matches is

  1. 33.25
  2. 32.25
  3. 34.25
  4. 34.50

  Answer :

  Option C

  Explanation:

  \begin{aligned}
  = \frac{(38.9 \times 10)-(42 \times 6)}{4}
  \end{aligned}
  
  \begin{aligned}
  = \frac{(1216 - 750)}{4} = 34.25
  \end{aligned}